Metal mercury tube switch



ea. 31, 19%. J. H. sTALEY METAL MERCURY TUBE SWITCH Filed April 24, 1953 JosephH. Swley,

Attorrwu.

' Patented Dec. 31, 1940 UNITED STATES, PATENT OFFICE METAL MERCURY TUBE swn'cn Joseph H. Staley, Columbus, Ind. ApplicatiouApril 24, 1933, Serial N... 667,536 8 Claims. (01. 200-152) g This invention relates to the art of mercury tube switches for making and breaking electrical circuits. While the structure embodying the invention is adapted to be used in handling currents of low voltage, it is particularly adapted to higher voltages of comparatively heavy current flows.

A primary object of the invention is to provide a non-fragile structure capable of being manufactured at an extremely low cost and which will be durable and reliable .over a long period of time even though subjected .to occasional over-loads.

An important object of the invention is to provide a structure which will permit the mercury to remain in a pure state uncontaminated with a clean surface so that the mercury will remain frisky.

A further important object of the invention is to provide means for sealing the mercury container against the entrance of atmospheric gases and against the escape of a gas which may be employed within the container. In this regard the sealing means is employed not only to perform the ofiice of sealing against the flow of gases 2 but also to serve as an insulator separating one electrode from another. W

A still further important object of the invention is to provide means for definitely-locating the position of the are which occurs upon the 30 separation of the mercury at the time of interrupting the electrical circuit.

These and other objects and advantages of the invention will. become apparent to those skilled in the art'in the following description of the in- 35 vention as illustrated in one particular form, in

which Fig. 1 is a side elevation of a structure embodying my invention;

Fig. 2, an end elevation;

40 Fig. 3, a top plan view;

Fig. 4, a longitudinal vertical section through the structure in a position rocked to the "01? position;

Fig. 5, a transverse section on the line 55 in Fig. 6, a central longitudinal section similar to Fig. 4 but'rocked to the on position; and

Fig. '7, a detail in vertical section of a modified structure. 1

60 Like characters of reference indicate like parts throughout the several views in the drawing.-

My invention contemplates the use of a metallic walled member within which mercury may be caused to flow from one end to the other upon 6 longitudinal rocking of the member. I employ the metal walled member primarily on account of the fact that it does not become broken under the ordinary usage as is often the case with the glass walled members heretofore employed. In the form of my invention as illustrated by the 3.0- 6 companying drawing, 1- form a metallic tube l0 closed at one end and open at the other. Around the outer side of the tube at its open end are formed screw-threads. An insulating plug or bushing I I is formed to fit tightly within the open m end of the tube, preferably by a forced fit so as to make a sealing connection circumferentially around it against the inner wall of the tube.-

This plug H has an axial bore therethrough of two diameters, and a stud i2 is initially pressed through the smaller bore to have its major length projecting outwardly beyond the outer face of the plug. The under side of the head of the stud-is preferably formed to be conical and the end, of the larger bore is likewise conically formed so that go the head may be seated thereagainst with a close lit. The inner or top face of the stud I2 is flat and forms a metallicface across the end of the bore.

A bushing l3 hereinafter termed a breaker, is formed out of some suitable insulating material, preferably refractory in nature so as to resist the effect of an electrical arc. This breaker I3 is formed with an outer cylindrical surface and an inner conical bore merging by the smaller end thereof into a cylindrical bore. The breaker I 3 is pressed within the larger bore of the plug II to have the breaker end having the cylindrical bore carried back within the plug and spaced a relatively short distance from the face of the head of the stud l2. The spacing between the inner end of the breaker l3 and the face of the stud l 2 is critical in that a circumferential pocket isfor-med therebetween within which a globule of mercury I4 is retained. The longitudinal length 40 of this pocket is made to be such by the spacing of the breaker l3 from the head of the stud l2 that when the assembled parts are rocked to some such position as indicated in Fig. 4, the globule of mercury I4 will remain within the pocket without an additional spilling over as will hereinafter be explained.

As above indicated, the plug l l with the stud l2 and the breaker l3 assembled therein is pressed into the open end of the tube In to have the shoulder presented around the annular flange l5 strike and bear against the end of the tube I 0.

A retainer ring I6 is formed to extend longitudinally over the flange I 5 and screw-threadedly engage the threads on the tube It). This ring l6 has an inturned flange coming into contact with the outer face of the plug H so that when the ring I6 is turned sufficiently about the end of the tube I0, this flange will tend to compress the plug flange I5 longitudinally against the end of the tube I0.

The plug II on its outer end about the stud I2 is counter-bored to form a conical depression within which is seated a conical sealing washer I1 which is passed over the end of the stud I2 and compressively forced against the plug I I by means I of a lock nut I8, this nut tending to compress the plug II between the head of the stud I2 and the washer I1 and further tending to force the plug II laterally against the tube III and the retaining ring IS. The diameter of the washer I1 is less than that of the diameter of the opening through the ring It so that there is an annular gap therearound between the washer and the ring.

The mercury tube switch assembled as above indicated is carried by some suitable base It! by having the tube III compressively engage between the spring clips 20 and 2I and the stud I2 entered through an eye of an upturned clip'221. A nut 23 screw-threadedly carried on the stud l2 and abutting the nut I8 is brought into contact against the back side of the clip 22 when the nut 24 is screw-threadedly carried on the outer end of the stud I2 and revolved thereon to compressively engage the clip 22 between it and the nut 23. The clips 20 and 2| are united at their lower ends and fixed to the base I9 to be-in an electrical circuit with a conductor 25. The clip 22 is in electrical circuit with the conductor 26, the switch assembly being thus interposed between the two conductors 25 and 26 as a means of making and breaking the electrical circuit therebetween. The base I9 is mounted in any suitable manner (not shown) whereby it may be rocked to shift the switch assembly from one position to another as indicated in Figs. 4 and 6.

An important factor contributing to the success of the operation of the switch is that the atmospheric gases within the tube Ill be replaced by some gas inert insofar asmercury'is concerned.

It is therefore necessary to remove the atmos 4 pheric gases at the time the tube III is sealed by the plug II and furthermore to replace such removed gases by the gas to be employed. Hydrogen gas operates successfully. The quantity of mercury 21 which is placed in the tube III prior to the insertion of the plug I I is such that when the switch assembly is rocked to its extreme position of closing the circuit, there will be suflicient mercury to bridge over the breaker I3 through its axial bore to be in contact'both with the face of the head of the stud I2 and over an appreciable area of the inner side of the wall of the tube III as indicated in Fig. 6. In practice this quantity of mercury is made to be such that the electrical circuit between the stud I2 and the tube III through the mercury is maintained even though the tube be turned completely on its end with the stud I2 pointing downwardly. However, the proportions of the parts entering into the switch assembly are such that when the parts are rocked to the normal position to complete the circuit through the mercury 21 between the stud I2 and the tube III, the cylindrical bore in the breaker I3 is completely filled by the mercury, but upon reverse rocking, at the instant of the break, the upper portion thereof is open as indicated in Fig. 6, so as to leave a clear passageway leading from that part of the circumferential chamber above the mercury between the breaker and the stud I2.

The breaker I3 while being carried within the plug II is formed to have sufficient length so as to extend beyond the plug II an appreciable distance into the tube III with clearance therearound. I

Due to the overhang cf the breaker I3 beyond the plug II within the tube I0, the'mercury 21, Fig. 6, will flow around under the overhanging part of the breaker against the end of the plug I I to fill up that space while more of the mercury flows through the conical bore of the breaker I3 against the head of the stud I2.

Now. when the switch is rocked to the off position, Fig. 4, the mercury 21 will tend to flow to the other end of the tube III away from the breaker I3. In so doing the globule I4 is left within the pocket formed between the breaker I and the head of the stud I2 and as above indicated, this pocket is of a definite size such that when the mercury 21 initially flows away from the globule I4 left b'ehind, the additional rocking of the switch to insure sufficient elevation of the then raised end of the tube to cause the larger mass of mercury to remain at the lower end, will not cause any mercury to break away from the globule I4 and flow through the breaker I3 to momentarily .re-establish the circuit. In other words, once the major mass of the mercury 21 leaves the globule I4, there is no additional spill over from the globule I4 which would otherwise cause a flicker in the circuit. While the circuit is interrupted principally by elevating the end of the tube within which the plug I I is fitted so as to cause a mechanical separation of the mercury under the influence of gravity, other I factors enter which cause the arc produced at the time of separating these masses of mercury to come at a definite location. In order to have long life, it is necessary that there be no pitting or wearing away of the metallic surfaces of the tube III and of the exposed head of the stud I2. Should there be any deterioration of these metallic surfaces, the-metal eroded would become amalgamated with or coated over the mercury so that its original inherent high surface tension would be destroyed and there would no longer be a sharp break between the globule I4 and the main mass of t e mercury. Therefore it is essential that the are produced beconfined within the breaker I3 which is made of a suitable refractory material to withstand the action of the arc.

In shifting from the position indicated in'Fig. 6 to that indicated in Fig. 4, the mercury tends to flow down the bore within the breaker I3 until the thickness of the mercury is'reduced to produce an actual severance thereof substantially Thus the are joccurcury at the time they are severed is initiallydocated at this position. .Since the mercury within the cylindrical bore of the breaker I3 represents that section having the smallest cross-sectional area, the natural inherent effect of the current flowing through the mercury is to set up a pinching effect tending to, automatically pinch this narrow neck of mercury so as to further restrict its cross-sectional area. This action is accentuated by reason of the metallic wall of the tube I0 encircling the breaker causing an intensification of the magnetic field setup therearound. 'Thus the flow of current itself tends to quicken the break between the two masses of mercury in addition to the'efiect of gravity and the surface tension of the mercury.

Now when the arc does occur, it takes place at the small end of the breaker I 3 wherein by reason of the restricted surface, the surface immediately about the arc becomes, highly heated and the gases thereabout tend to expand. Since the pocket between the breaker and the head of the stud I2 is limitedin size, the expansion must be out through the breaker into the increasingly larger surface and consequently cooler surface so that there is a tendency of the expanded gases to flow inwardly into the tube III thereby carrying the ionized gases into a cooler area'where the tendency is to cause the gases to become deionized and thereby reduce the possibility of the re-establishment of the current through the spacebetween the globule of mercury I4 and the receding mass 21.

Since the breaker I3 overhangs the plug I I, and

since the mercury is coming down and out of the breaker I3 when that end of the tube is being 'lifted, the mass of mercury 2'! covers over the surface of the tube III immediately about the overhanging end of the breaker I3 so that even should the arc occur at the outer end of the breaker I3, it will not be in contact with the metallic wall of the tube but will still have to be between two separating masses of mercury. Furthermore as the tube is being rocked to the position indicated in'Fig. 4, there is still a mass of mercury back under the overhanging portion of the breaker I3 which rushes along in-conjunction with the other mercury coming out of the' breaker so as to form in effect a delayed covering over of the tube I until allthe mercury to come has been emptied from within the breaker, the combined effect being not only to effectively cover over the wall of the tube I0 but to accelerate the fiow of mercury to the opposite end of the tube.

As to materials employed, I find that the tube I0 and the stud I2 forming theother electrode may be made out of any metal which does not amalgamate with the mercury. Iron, cold rolled steel, and stainless steel have been employed successfully. The plug I I must be made out of some material which will not shrink, which will not contaminate the mercury and which may be machined or molded. One suitable material which I have employed is a vulcanized paper fiber although care must be exercised to. control the moisture content thereof. The material from which the plug I I is made may preferably have some degree of resilience although it must be non-deteriorating so that the essential feature of forming a gas tight connectionbetween the tube Ill and the stud I2 is maintained at all times. The breaker I3, being fragile, is supported by the plug II so that the breaker may expand and contract and may be cushioned from external shocks without liability of breakage.

The foregoing described structure provides for the chamber I back of the breaker so that a pool I4 of mercury may be formed in order that the circuit is broken between twomasses of mercury. This is preferable when the current flow is such that the interruption thereof between the walls direct would cause pitting of the metal. For circuits having less flow, the chamber I5 may be omitted entirely as shown in Fig. 7 where the breaker is pushed into the plug bore to have the breaker end bear against the larger bore end whereby there is no chamber left therebetween. In this form, it is to be seen that the gas pressure induced by the heat of the arc may be greatlyincreased in the small bore of the breaker since,

conditions, the size decreasing to nothing as shown in Fig 7. When the chamber I 5 is necessary, the

breaker shape provides in effect a Venturi tube between the chamber I5 and the larger chamber in the tube III. I

While I have here shown and described my invention in the one form as now best known to me, it is obvious that structural changes may be made without departing from the spirit of the invention and I therefore do not desire to be limited to that precise form beyond the limitations as maybe imposed by the following claims.

I claim:

1. In a mercury tube switch, the combination of a metallic tube closed at one end, an insulating plug sealably fitted in the open end of the tube, an electrode sealably carried by the plug and terminating interiorly thereof to extend across the end of an axial bore in the plug, a breaker axially carried in said bore defining a short cylindrical chamber between the breaker and the electrode, said breaker having a bore therethrough flaring outwardly toward the rear end from a thereover between said tube and said electrode upon tilting of the switch to lower the electrode, a retaining ring interengaging said tube and said plug to prevent axial shifting of the plug in the tube, and cooperating means compressively engaging said plug tending to distort'theplug and maintain sealing joints between the plug and the electrode and theplug and the tube.

2. In a mercury tube switch, the combination of a metallic tube closed at one end, an insulating plug sealably carried in the open end of the-tube, an electrode entering said plug and extending interiorly thereof into a chamber in the plug, from which chamber an axial bore leads to discharge at the rear of the plug, said bore having a diameter at the chamber end less than that of the small axial opening leading from said chamber,-

chamber and a diameter at the rear end exceeding that at the chamber end, a quantity of mercury ing said tube and said plug to prevent axial shifting'of the plug in the tube, and cooperating means compressively engaging said plug tending to urge the plug into compressive contact with the tube and the electrode.

3. In a mercury tube switch, the combination of a metallic tube closed at one end, an insulating plug sealably carried in the open end of the tube, an electrode extending into the plug to enter a chamber therewithin, from which chamber leads an axial bore to discharge from the rear of the plug, said bore having a diameter at its chamber end less than the transverse Width of the chamber and having a diameter at its rear end larger than at the chamber end, and a quantity of mercury sufficient to interconnect the tube and the electrode through the bore upon tilting the switch to lower the electrode, and a breaker carried by the plug in which said bore is located, said breaker being axially mounted in the plug to extend rearwardly therefrom a distance and. formed tohave the external diameter of the extension less than that of the tube so as'to leave a clearance therearound.

4. Ina mercury tube switch, a metallic tubular member, an insulating plug' sealably carried in one end of the member, said plug having an axialv bore therethrough having a .small diam eter in that portion adjacent the outer end and a larger diameter toward the rear end, an electrode inserted through said bore, a head on the electrode within the larger diameter portion of the bore limiting withdrawal of the electrode, a compression member carried externally by the electrode causing the plug to be compressively engaged between the head and the compression member, and a quantity of mercury sumcient to interconnect the tubular member and. the electrode head through said bore, said head being spaced forwardly in said bore to leave a chamber as defined by the bore between the head and the rear end of the plug, said head and said compression member having opposing conical faces engaging like faces on the plug, whereby a lateral deformation of the plug is induced to urge the plug against the tubular member.

5. In a mercury tube switch, a metallic tubular member, an insulating plug sealably carried in one end of the member, said plug having an axial bore therethrough having a small diameter in that portion adjacent the outer end and a larger diameter toward the rear end, an elec- ,trode insertedthrough said bore, a. head on the electrode within the larger diameter portion of the bore limiting withdrawal of the electrode, a compression member carried externally by the electrode causing the plug to bev compressively engaged between the head and the compression 6. In a mercury tube switch, the combination of a metallic tube closed at one end, an insulating plug sealably fitted in the open end of the tube, an electrode sealably carried by the plug and terminating interiorly thereof to extend across the end of an axial bore in the plug, a breaker of refractory material axially carried in said bore defining a short cylindrical chamber between the breaker and the electrode, said breaker having a bore flaring outwardly toward the rear end from a small cylindrical bore of relatively short length leading directly from said chamber, a quantity of mercury sufficient to bridge over said breaker to complete a'circuit thereover between said tube and said electrode upon tilting of the switch to lower the electrode and adapted to separate adjacent the cylindrical bore of the breaker when the tube is tilted in the opposite direction.

7. In a mercury tube switch, the combination of, a metallic tube closed at one end, a resilient insulating plug sealably fitted in the open end of the tube, an electrode sealably carried by the plug and terminating interiorly thereof to extend across the end of an axial bore in the plug, a

breaker of refractory material axially carried in said bore and defining a short cylindrical chamber between the breaker and said electrode, said breaker having a bore flaring outwardly and rearwardly, and a quantity of mercury suflicient to bridge through said breaker bore to complete a circuit between said tube and said electrode upon tilting of the switch.

8. In a mercury tube switch, the combination of a metal tube closed at one end, an insulating plug sealably fitted in the open end of the tube, an electrode sealably carried by the plug and terminating interiorly thereof to extend by a head across the inner end of an axial bore in the plug, a breaker of refractory material within said tube and maintained by said plug in axial end to end abutment with the inner end of said electrode head, said breaker having a bore fiaring outwardly toward its rear end, a quantity of mercury sufficient to bridge over said breaker to complete a circuit thereover between said tube and said electrode upon tilting of the switch to lower the electrode and adapt it to separate adjacent the cylindrical bore of the breaker when the tube is tilted in the opposite direction.

JOSEPH H. STALEY. 

